Minor wording changes

Just eliminates doubling of "use, uses" for better clarity.

Author: sspencerwire

docs/books/admin_guide/03-commands.md

@@ -538,7 +538,7 @@ total 1332
 -rw-r--r--.  1 root root    283 18 may.  17:05 mtab
 ```
 
-* List `/var` files larger than 1 megabyte but less than 1 gigabyte, the example here uses the advanced use of the `grep` command - regular expressions. Novices don't have to struggle too much, there will be a special tutorial to introduce these regular expressions in the future.
+* List `/var` files larger than 1 megabyte but less than 1 gigabyte. The example here uses advanced `grep` commands with regular expressions. Novices don't have to struggle too much, there will be a special tutorial to introduce these regular expressions in the future.
 
 ```bash
 $ ls -lhR /var/ | grep ^\- | grep -E "[1-9]*\.[0-9]*M"